The structure of ‘Hemidesmosomes’ contain intracellular proteins including ‘plectin’ and ‘BP230’.
Plectin (HD1) is a 500-kd protein which binds intermediate filaments.
BP230 (also termed as BPAG1) is a 230-kd protein which has homology to both desmoplakin and plectin. BP230, like plectin, functions in the connection between ‘hemidesmosomes’ and ‘intermediate filaments’.
Hemidesmosomes also contain the intracellular portions of the transmembrane proteins collagen XVII (BP180) and alpha-6-beta-4 (α-6-β-4) integrin. The β-4 integrin subunit performs a central role in hemidesmosome formation and contains an especially large cytoplasmic domain, which interacts with other proteins of the hemidesmosomal plaque. Collagen XVII is a transmembrane collagenous protein which interacts with α-4 integrin and BP230 intracellularly and with laminin 5 extracellularly.